EQUINE VETERINARY EDUCATION / AE / MARCH 2015
129
of TMJ disease (Baker 2002). An equine study showed that dental floating increases the range of motion of the TMJ in the rostrocaudal direction, but no specific dental abnormalities were correlated to this increased TMJ mobility (Carmalt et al. 2003). Dental pathology has been shown not to affect the proinflammatory cytokine profile of TMJs of horses, thereby suggesting that dental irregularities do not result in TMJ OA (Carmalt et al. 2006). An increased frequency of TMJ disease has been seen in human patients who require orthognathic surgery (Abrahamsson et al. 2009). Malocclusions in human patients can be a contributing factor to TMJ disease (Henrikson and Nilner 2003), but in our equine population this still has to be confirmed. Considering the potential relationship between dental and TMJ pathology, a full oral examination with correction of all dental imbalances and abnormalities in horses with TMJ disorders is still recommended (Baker 2002). It is documented that bit-induced pain can cause the
same signs as TMJ disease (Cook 1999) and often a high level dressage horse, such as the horse in the present report, carries a heavy bit. Considering the owner reported having tried different bits already and since blocking the TMJ was positive and pathology was seen on CT scan, the authors are convinced that this horse did indeed suffer from TMJ disease. However, whether a heavy bit can induce TMJ disease is unknown. In a recent study, the inflammatory response after LPS
injection in equine TMJs and metacarpophalangeal joints were compared. All injected joints showed clinical signs of inflammation, horses were lame in the injected limbs, but all horses continued eating independently of TMJ inflammation (Carmalt et al. 2011), suggesting that more pathology may be needed before signs occur, or that signs only occur under particular conditions, e.g. riding. Faster attenuation of the inflammatory response (cytokines) was seen in the TMJs compared to the metacarpophalangeal joints, suggesting the response in TMJs to inflammation might be somewhat different, from that seen in other joints (Carmalt et al. 2011). This might also be the reason why the horse in this report responded to just one joint treatment. Trends show that the proinflammatory cytokine profiles of equine TMJs change with age (Carmalt et al. 2006). In dogs and cats no relationship was seen between age and presence or severity of TMJ OA on CT scan (Arzi et al. 2013). In mice a relationship between initial stages of TMJ OA and increased activity of metalloproteinases in the articular cartilage of the mandibular condyles has been previously described (Gepstein et al. 2003), as well as in synovial fluid aspirates from human TMJ osteoarthritic patients (Kanyama et al. 2000) and in sheep TMJ synovial fluid in an experimental model (Miyamoto et al. 2002). Obviously, further research is needed to determine how age and inflammation affect the TMJ of the horse. In the present case, bilateral changes were seen on CT
(worst in the left TMJ). In dogs TMJ OA is often seen bilaterally on CT scan and in many of the canine patients these changes do not result in clinical signs (Arzi et al. 2013). As in any other joint, the clinical relevance of diagnostic imaging findings in TMJs should be confirmed with diagnostic analgesia. As evaluation of most diagnostic analgesic tests in clinical work is subjective, the risk of a placebo effect exists. Placebo effects have been shown in both caregivers and veterinarians in studies evaluating osteoarthritic dogs’ response to treatment (Innes et al. 2003; Conzemius and Evans 2012). Therefore, the risk of a rider and veterinarian placebo effect cannot be fully
rejected. Nevertheless, professional riders are generally very critical about the performance of their horses. It appears to the authors that the treatment had a beneficial effect since the horse and rider definitively responded positively to the diagnostic block and treatment. The owner now reports the absence of symptoms and that the competition results of the horse have improved considerably. To the best of our knowledge, no studies have been
performed evaluating the best joint treatment for equine TMJ OA. Triamcinolone and hyaluronic acid were chosen as these are well recognised treatment choices for OA in equine high motion joints (Ferris et al. 2011). In sheep with induced OA of the TMJ, hyaluronic acid joint treatments minimised the extent of OA changes significantly compared to controls (Neo et al. 1997). Furthermore, hyaluronic acid is used in human TMJ patients (Manfredini et al. 2010). Other intra-articular treatment options could have been other corticosteroids (methylprednisolone or betamethasone esters), polysulphated glycosaminoglycans and ACS (autologue conditioned serum). Furthermore, systemic treatment with NSAIDs could be added to the treatment regime. In man it seems less common to use intra-articular medications. Treatment regimes range from exercises, medication and splints to arthrocentesis, arthroscopy and, more drastically, discectomy and joint replacements (Ingawale and Goswami 2009; Reid and Greene 2013). In conclusion, this case emphasises the importance of investigating whether TMJ disease is responsible for a reduction in the performance of equine athletes. More prevalent problems such as lameness should always be investigated first. In our experience, a very sensitive rider is required to detect the tiny changes in performance and behaviour and, furthermore, CT scanning and diagnostic analgesia are necessary to diagnose subtle changes of the TMJs, which in this case caused a reduced performance in a high level dressage horse. Further studies in TMJ symptomatology, pathogenesis and outcome of treatment are needed.
Authors’ declaration of interest No conflicts of interest have been declared.
Manufacturers’ addresses
1Philips Healthcare, Malmö, Sweden. 2Ab Solving Oy, Pännäistentie 181, Pietarsaari, Finland. 3Pharmaxim AB, Stenbrovägen 32, Helsingborg, Sweden. 4Orion Pharma AB, Animal Health, Sollentuna, Sweden. 5Astra Zeneca, Arne Jacobsens Allé 13, København S, Denmark. 6Bristol-Myers Squibb, Lyngby Hovedgade 98, Lyngby, Denmark. 7Scanvet, Kongevejen 66, Fredensborg, Denmark.
References
Abrahamsson, C., Ekberg, E., Henrikson, T., Nilner, M., Sunzel, B. and Bondemark, L. (2009) TMD in consecutive patients referred for orthognathic surgery. Angle Orthod. 79, 621-627.
Arzi, B., Cissell, D.D., Verstraete, F.J., Kass, P.H., DuRaine, G.D. and Athanasiou, K.A. (2013) Computed tomographic findings in dogs and cats with temporomandibular joint disorders: 58 cases (2006-2011). J. Am. Vet. Med. Ass. 242, 69-75.
Baker, G.J. (2002) Equine temporomandibular joints (TMJ): morphology, function and clinical disease. Proc. Am. Ass. Equine Practnrs. 48, 442-447.
Barnett, T.P., Powell, S.E., Head, M.J., Marr, C.M., Steven, W.N. and Payne, R.J. (2014) Partial mandibular condylectomy and temporal
© 2014 EVJ Ltd
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88
